A traditional liquid crystal display comprises a display panel and a backlight module including a backlight source and a control system. At present, backlight sources are generally white LED backlight sources. White light LEDs can be mainly classified into types of Bchip+Y powder (blue light chip+yellow phosphor powder) LEDs, Bchip+Y σ powder (blue light chip+red and yellow phosphor powder) LEDs, Bchip+RG powder (blue light chip+red and green phosphor powder) LEDs, BGchip+R powder (blue and green light chips+red phosphor powder) LEDs, and RGBchip (red, green and blue light chips) LEDs, for which color representation capabilities increase in order.
In the industry, the color representation capability specifications for liquid crystal displays are classified into the following from low to high: NTSC (National Television Standards Committee) below 72%; NTSC 72%, sRGB 100% matching rate (standard Red Green Blue 100% matching rate, hereinafter sRGB 100%), and Adobe 100% matching rate (hereinafter Adobe 100%).
sRGB 100% and Adobe 100% are both high-end product requirements with the standard chromaticity coordinates of red primary color, green primary color and blue primary color as shown in the following Table 1; red primary color and blue primary color have the same specification under the two standards while green primary color has different specifications; green primary color applying Adobe specification has wider color gamut range than that applying sRGB specification, and the color representation capability for sRGB specification can only correspond to 74.1% of Adobe specification.
TABLE 1Adobe standardsRGB standardChromaticity coordinatesxyxyRed primary colorR (Red)0.6400.3300.6400.330Green primary colorG (Green)0.2100.7100.3000.600Blue primary colorB (Blue)0.1500.0600.1500.060NTSC Gamut95.5% 70.8%Adobe100% Matching Rate100%74.1%sRGB100% Matching Rate100% 100%
NTSC Gamut refers to the ratio of the area of a triangle formed by chromaticity coordinates (x, y) of RGB of a practical product to the area of a triangle formed by chromaticity coordinates (x, y) of standard RGB primary colors of NTSC; the sRGB 100% matching rate refers to the ratio of the overlapping area between a triangle formed by chromaticity coordinates (x, y) of RGB of a practical product and a triangle formed by standard RGB chromaticity coordinates (x, y) of sRGB to the area of a triangle formed by chromaticity coordinates (x, y) of standard RGB primary colors of sRGB; and Adobe 100% Matching Rate is the ratio of the overlapping area between a triangle formed by chromaticity coordinates (x, y) of RGB of a practical product and a triangle formed by standard RGB chromaticity coordinates (x, y) of Adobe to the area of a triangle formed by chromaticity coordinates (x, y) of standard RGB primary colors of Adobe.
A color is represented by chroma and brightness together. Chroma is used to evaluate color quality stimulation with a value expressed by chromaticity coordinates generally. Brightness refers to the bright degree of a picture with a unit of candela per square meter (cd/m2) or nits. x, y in Table 1 represent chromaticity coordinates respectively; and in the table, chromaticity coordinates of red primary color (Red), green primary color (Green) and blue primary color (Blue) corresponding to Adobe specification and sRGB specification are given, and color representation capabilities corresponding to Adobe specification and sRGB specification conditions are given as well.
sRGB 100% can be realized with Bchip+RG powder LEDs, but the matching rate of Adobe 100% is much less than 100%. It is a main method for realizing Adobe 100% to replace Bchip+RG powder LEDs with GBchip+R powder LEDs. However under the same power consumption, the overall light efficiency for GBchip+R powder LEDs is low; its light flux will be decreased by more than a half with comparison to Bchip+RG powder LEDs. Although color filters with GBchip+R powder LEDs have a transmittance increased by about 8% than color filters with Bchip+RG powder LEDs, the overall brightness of the liquid crystal displays has still about loss over 46%.